While the Tuesday-night announcement surprised Perry's staffers and supporters—even following a disappointing fifth-place finish in the Iowa caucuses—his abrupt and public change of heart on Wednesday morning caught them completely off guard.

So what could he be thinking? We asked seasoned strategists, politicos, and Republican experts on the ground in early primary states for their top five theories.

1. In the light of day, those top four Iowa finishers don’t look so hot.

Massachusetts Gov. Mitt Romney, still the perceived GOP front-runner, can hardly break 25 percent in the polls. And the three other anti-Romney candidates trailing him have their own fundamental flaws—flaws Perry must think will keep them from a real shot at the nomination.

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Former House Speaker Newt Gingrich, who finished in fourth on Tuesday night in Iowa, has a temperamental past littered with fodder for opposition researchers and may not have the money to dig himself out of that hole.

Rep. Ron Paul of Texas, who came in third, has the grassroots organization and the money—but his message, particularly on foreign policy, is wildly out of step with establishment Republicans.

Second-place finisher and former U.S. Sen. Rick Santorum flies his social-conservative flag high. But he might just be too conservative to win. He believes, among other controversial stances, in allowing states to outlaw birth control and has said he opposes gays serving openly in the military in part because soldiers “shower together.” Despite his recent surge, Santorum may not have the necessary means to compete in a broad field, political operatives say. “It’s unclear whether Santorum can cobble together the resources, the fundraising, to make a push beyond Iowa,” said Ford O’Connell, a Republican strategist who advised the McCain-Palin ticket in the last presidential race.

Perry may figure that with more money, a strong track record with evangelicals, and a warm reception among military veterans, he could pull off a win in the first Southern state primary in South Carolina, even after his Iowa finish.

"Clearly in the light of day (and a decent night sleep) he realized that Santorum hasn't been run through the political meat grinder yet," said GOP strategist Mary Matalin. "Who knows where this thing will be by [South Carolina], where Perry still commands support."

2. The Iowa caucuses aren’t foolproof.

Perry believes the Iowa caucuses are a screwy, nonrepresentative endeavor. In some ways, he’s right. Turnout at caucuses is far lower than at primary elections; only the most committed politicos show. In Iowa, Democrats and independents can cross the aisle to participate—a boon to a candidate like Paul, who has hefty support outside the Republican Party, or to Romney, who’s considered the most moderate of the front-runners.

The first-test Iowa caucuses haven’t historically been a perfect predictor. Sen. John McCain of Arizona finished fourth there in 2008 but went on to clinch the GOP nomination. So much for the theory that there are only three tickets out of Iowa. George H.W. Bush finished third there in 1988 but still became the Republican nominee and then the president.

“This is a quirky place and a quirky process to say the least,” Perry said on Wednesday, before leaving Iowa. “We’re going to go into, you know, places where they have actual primaries and there are going to be real Republicans voting.”

3. The media loves a "comeback kid" story, and South Carolina could be just the place for it.

With a third-place finish in the Iowa caucuses, Paul should’ve been the Texan getting the attention on Wednesday morning. Instead, Perry managed again to steal the show, announcing via Twitter his unexpected decision to stay in the race.

If he can stay in the headlines in South Carolina, he could monopolize the free media needed by Santorum, the other white evangelical candidate who is intriguing to social conservatives but has limited resources. Even if he had the cash, there's little ad space left to buy there.

“South Carolina has epitomized the rationale of the Perry campaign,” said University of Texas political scientist Jim Henson. “Perry’s probably thinking if he’d had a couple of other months in Iowa, they would’ve seen the light there like he hopes they’re going to in South Carolina.”

4. Maybe the clumsy Rick Perry of the last few months is the anomaly.

Sure, he has had high-profile gaffes and debate meltdowns. But maybe these early stumbles were uncharacteristic—signs of unpreparedness that the governor, a late arrival to the race, has since rectified. Just not in time for Iowa.

In the last couple of debates, Perry hasn’t had any royal embarrassments, although he has two more opportunities in New Hampshire in the next week. He has appeared to hit his stride in recent weeks campaigning in Iowa, a state he set up shop in later than other candidates. There have been major shake-ups among campaign staffers (Perry wouldn’t rule out even more of them on Wednesday, saying he would leave that to campaign manager Joe Allbaugh). He may think the effects of the changes will show up a little farther down the road and that dropping out now would be premature.

5. He doesn’t want to pull a Tim Pawlenty.

One thing is apparent from Santorum’s strong finish on Tuesday night: Social conservatives are pining for an anti-Romney to coalesce behind. Stick around long enough in this GOP horse race, and almost every candidate gets a resurgence. That's something GOP strategist O’Connell says former Minnesota Gov. Tim Pawlenty—who dropped out in August after a third-place showing in the Iowa straw poll—“has got to be kicking himself over.”

“If Tim Pawlenty was still around, he would’ve seen a surge he could’ve capitalized on,” O’Connell said.

He’s not. And that provides an opening for Perry in South Carolina—but only if he plays his cards perfectly, which he has yet to do.